Eco-physiological Responses Of Mangrove Plant Kandelia Obovata Seedlings To Dibuthyl Phthalate And Diethyl Phthalate Stress

Phthalate esters (PAEs) have been the most widespread contaminant as the mass producedand used of plastic products worldwide in recent years. Growing in the intertidal zones of bayestuary areas which were between the tropical and sub-tropical land and sea, mangroves playedan important role in the coastal estuarine ecosystem. Ecology pollutions have been one of themost important problems in the study of mangroves currently, but there’s no deeply researchabout the environmental behavior and biological effects of the PAEs. In this paper, we discussedthe eco-physiological responses of mangrove plant Kandelia obovata seedlings to dibuthylphthalate and diethyl phthalate stress. The propagules of Kandelia obovata Sheue, Liu&Yongwere cultivated in sand and treated with15‰artificial seawater for180days under thelaboratory conditions. The influence of increasing concentrations of Dibuthyl phthalate andDiethyl phthalate (0,0.02,0.2,2,5,10mg/L) on seedling germination, growth and membraneprotection system were observed to inquire into the eco-physiological responses of mangrove K.obovata to PAEs phytotoxicity. Results were as follows:Effect of Dibuthyl phthalate (DBP) and Diethyl phthalate (DEP) different concentration onseedling germination of mangrove K. obovata is obvious. It showed no significant difference onhypocotyl germination from control group for DBP, but a significant inhibition on the secondpair of leaves; when at concentration of10mg/L, inhibition occurred on the first pair of leaves.As for DEP, when at concentration of5mg/L, it showed a significant inhibition on the leavesunfolding; at concentration of10mg/L, it showed a significant inhibition on the seedlinggermination. PAEs had a significant inhibition on the seedling germination at the highconcentration of10mg/L, and DBP had stronger inhibition on germination than DEP.There’s a significant promotion on the height growth at0.2,2mg/L of DBP and0.2,2,5mg/L of DEP, on the crown width at2,5mg/L of DBP and0.2,2,5mg/L of DEP, on the rootlength at0.2,2,5mg/L of DBP and5,10mg/L of DEP, on the leaf area at0.2,2,5mg/L of DBPand0.02,0.2,2,5mg/L of DEP, on the fresh weight which is at0.02,0.2,2,5mg/L of DBP and2,5mg/L of DEP for root, at2,5mg/L of DBP and0.2,2,5mg/L of DEP for leaf, at2mg/L ofDBP and2,5mg/L of DEP for total fresh weight, but a significant inhibition on the leaf area at10mg/L of DBP. There’s a significant promotion on dry weight as well, at2,5mg/L of DBP and DEP for root, at0.2,5mg/L of DBP and0.02,0.2,2,5mg/L of DEP for leaf, at2,5mg/L ofDBP and5mg/L of DEP. DBP showed more significant promotions on crown width, root length,leaf area and root fresh weight than DEP.With increasing concentrations of DBP and DEP, an increase in the chlorophyll content (chla,chlb and chla+chlb), trends showed increasing at low and medium concentration, but decreasingat high concentration for DBP and continued increasing for DEP, which suggested stimulatoryeffect of PAEs. The extent of promotion by DBP was also greater than DEP.It showed a significant promotion on MDA content in leaves between control and treatedgroup, while at2mg/L of DBP and0.02,2mg/L of DEP in roots. Trends showed increasing atlow and medium concentration, but decreasing at high concentration. Maximum in the mediumconcentration at2,5mg/L. The extent of promotion on root was greater at0.02,2mg/L by DEPthan DBP.It showed a particularly significant promotion on POD total activity, at0.02,0.2,2,5mg/Lof DBP and0.02,0.2,2mg/L of DEP for leaf, at0.02,0.2,2,5mg/L of DBP and DEP for root.The extent of promotion was greater by DBP than DEP. At the concentration of0.2,2,5mg/L ofDBP and5mg/L of DEP.There’s a significant promotion on SOD total activity in leaves, while at0.2,2mg/L of DBPand0.02,0.2mg/L of DEP in roots. But a significant inhibition in both leaves and roots at thehigh concentration of5mg/L. The extent of promotion was greater by DBP than DEP.There’s a particularly significant promotion on CAT total activity at0.2,2,5,10mg/L ofDBP and DEP in leaves, while at5mg/L of DBP and2mg/L of DEP in roots. But a significantinhibition at0.02,0.2mg/L of DBP and5,10mg/L of DEP. The extent of promotion was greaterat0.02,0.2,2,10mg/L on leaf and0.2,2mg/L on root by DEP than DBP, but at5mg/L DBPwas greater than DEP.Trends showed increasing at low and medium concentration, but decreasing at highconcentration, and the biggest promoted was in medium concentration of all the three protectiveenzymes. The total activities of POD, SOD in roots were even higher than in leaves, and CATtotal activity in roots was lower than in leaves.Detection of DBP in leaf and root tip of mangrove K. obovata seedlings. DBP content in rootis more than leaf, which reveals root is the key absorption and accumulation parts of K. obovataseedlings. Excepting high concentration (10mg/L), there’s no detection of DEP. It showed thatDBP is more easily absorbed and accumulated than DEP.